Moisture separator, and vapor generator

ABSTRACT

A moisture separator  100  includes a plurality of flat frame plates  102  disposed parallel to each other to define a plurality of zigzag passages  101  between the frame plates  102 , side walls facing the upstream side of the passages  101  defining entrance openings  120   a  and  122   a  of droplet collecting pockets  120  and  122.

FIELD OF THE INVENTION

[0001] The invention relates to a steam generator used in a steamgenerator of a pressurized water nuclear plant.

BACKGROUND ART

[0002] In a pressurized water nuclear power generating plant a reactorcore which is disposed within a reactor nuclear vessel is cooled byprimary cooling water. The primary cooling water, heated by the nuclearenergy emitted from the reactor core, is introduced into a steamgenerator. Within the steam generator, the heat is transferred tosecondary cooling water to boil the secondary cooling water. The steamthus generated drives a steam turbine to generate electric power. Thesteam generated within the steam generator is introduce into a steamseparating device, disposed in upper inside volume of the steamgenerator, for removing the water contained in the steam flow. The steamseparating device generally comprises centrifugal steam separatorsdisposed at the upstream side relative to the steam flow and a frameplate type moisture separator disposed at the downstream of thecentrifugal steam separators.

[0003]FIG. 5 shows an example of the conventional frame plate typemoisture separator.

[0004] In FIG. 5, a moisture separator 10 comprises a plurality of frameplates 12. A plurality of zigzag passages 11 are defined between theframe plates 12. Each of the frame plates 12 for defining the passages11 includes a plurality of droplets collecting pockets 14 disposed sidewall portions 12 a extending from roots 16, which swell outwardlyrelative to the zigzag passage 11, toward apexes 18 which swell inwardlyrelative to the passage 11. The steam including droplets W is suppliedinto the passages 11 through the left ends, in FIG. 4, and dischargedthrough the right ends after the droplets W are trapped and removed intothe pockets 14.

[0005] Recently, reduction in moisture at the outlet of the steamgenerator is required. However, there is a problem that the conventionalmoisture separator 10 cannot reduce the degree of wetness sufficiently.That is, the conventional moisture separator 10 has a problem that thedroplets collecting pockets disposed at the upstream sides in thepassages 11 can collect relatively large droplets W, however, so calledcarry over is occurs so that the droplets which were once trapped by thepockets 14 fly out of the pockets into the steam flow in the passage 11or the relatively small droplets W cannot be trapped sufficiently by thepockets 14 disposed at the downstream side in the passage 11.

SUMMARY OF THE INVENTION

[0006] The invention is directed to solve the above described problemsof the prior art and to provide a moisture separator improved toincrease the droplets collection performance.

[0007] Further, the objective of the invention is to provide a moistureseparator which reduces its production cost.

[0008] Further, the objective of the invention is to provide a moistureseparator which can collect relatively small droplets.

[0009] According to the invention, there is provided a moistureseparator comprising a plurality of flat frame plates disposed parallelto each other to define a plurality of zigzag passages between the frameplates, side walls facing the upstream side of the passages definingentrance openings of droplet collecting pockets.

[0010] The production cost is remarkably reduces compared with moistureseparators according to the prior art by using flat frame plates.

[0011] According to the invention, there is provided a moistureseparator with a plurality of frame plates disposed parallel to eachother to define a plurality of zigzag passages, wherein the frame platescomprise flat plate members; the moisture separator comprising dropletcollecting pockets having entrance openings disposed in side wallportions of the zigzag passages between, seeing from the upstream sideof the passages, roots swelling outwardly relative to the passage andapexes swelling inwardly relative to the passage; and the dropletcollecting pocket including first droplet collecting pockets, disposedat the upstream side of the passages, for collecting relatively largedroplets, and second droplet collecting pockets, disposed at thedownstream side of the passages, for collecting relatively smalldroplets.

[0012] When the steam flows through the zigzag passages, the dropletscontained in the steam impinge against the side walls of the passages.At that time, a portion of the droplets enters the droplet collectingpockets and are trapped in the pockets. At the upstream side of thepassages, relatively large droplets are collected because large dropletsare easily trapped. Therefore, the first droplet collecting pockets forcollecting relatively large droplets are disposed at the upstreamsections of the passages. On the other hand, in the downstream sectionsof the passages, relatively small droplets stay still in the steam flowafter the large droplets are trapped. Therefore, the second dropletcollecting pockets for collecting relatively small droplets are disposedat the downstream sections of the passages. Hence, the dropletcollection efficiency in particular the collection efficiency for thesmall droplets can be remarkably increased by the arrangement of thefirst droplet collecting pockets for collecting relatively largedroplets disposed at the upstream sections and the second dropletcollecting pockets for collecting relatively small droplets disposed atthe downstream sections of the passages.

[0013] The entrance openings of the first droplet collecting pockets arepreferably disposed apart from the apexes in the side wall portionsbetween the roots swelling outwardly relative to the passage and theapexes swelling inwardly relative to the passage, and the entranceopenings of the second droplet collecting pockets are preferablydisposed adjacent the apexes in the side wall portions between the rootsswelling outwardly relative to the passage and the apexes swellinginwardly relative to the passage.

[0014] Means for agglomerating droplets may be disposed between thefirst and second droplet collecting pockets. The means for agglomeratingdroplets may comprise a coil member disposed to across the passage.

[0015] Further, according to another feature of the invention, there isprovided a moisture separator with a plurality of frame plates disposedparallel to each other to define a plurality of zigzag passages, whereinthe frame plates comprise flat plate members; the moisture separatorcomprising a plurality of droplet collecting pockets having entranceopenings disposed in side wall portions of the zigzag passages between,seeing from the upstream side of the passages, roots swelling outwardlyrelative to the passage and apexes swelling inwardly relative to thepassage; and the entrance openings of all the droplet collecting pocketbeing disposed adjacent the apexes in the side wall portions between theroots swelling outwardly relative to the passage and the apexes swellinginwardly relative to the passage.

[0016] Furthermore, according to another feature of the invention, thereis provided a moisture separator with a plurality of frame platesdisposed parallel to each other and a plurality of arcuate sectionsattached to the frame plates to define a plurality of serpentinepassages, wherein the frame plates comprise flat plate members; and themoisture separator comprising a plurality of droplet collecting pocketshaving entrance openings disposed in side wall portions of theserpentine passages between, seeing from the upstream side of thepassages, roots swelling outwardly relative to the passage and apexesswelling inwardly relative to the passage.

[0017] Furthermore, according to another feature of the invention, asteam generator which comprises one of the above-described moistureseparator, an inversed U-shaped tube bundle which uses the primarycooling water from a nuclear reactor as a heating medium and a pluralityof stem separators. Steam containing less moisture can be generated by asteam generator with the above-described moisture separator so as toeffectively prevent erosion at a turbine unit of a turbine generator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a diagram showing a single passage of a moistureseparator according to a first embodiment of the invention.

[0019]FIG. 2 is a diagram similar to FIG. 1 showing a second embodimentof the invention.

[0020]FIG. 3 is a partially broken perspective view of a moistureseparator.

[0021]FIG. 4 is a schematic section of a steam generator for apressurized water type nuclear power plant.

[0022]FIG. 5 is a diagram similar to FIG. 1 showing a moisture separatoraccording to a prior art.

THE MOST PREFERRED EMBODIMENT

[0023] With reference to the attached drawings, a preferred embodimentof the invention will be described below.

[0024] With reference to FIG. 3, an example of the steam generator usinga moisture separator according to the invention is shown. The steamgenerator 50 includes a tube bundle 54 which is disposed at the lowerpart of the inside volume of a pressure vessel 52 and immersed in thesecondary cooling water. The tube bundle 54 is formed into invertedU-shape, one end thereof being fluidly connected to a primary waterentrance chamber 53 and the other end being fluidly connected to aprimary water outlet chamber 55. A plurality of centrifugal steamseparators 56 are disposed at the upper part of the inside volume of thepressure vessel 52 above the tube bundle 54, in particular above thesurface of the secondary water contained in the pressure vessel 52. Amoisture separator 60 is disposed above the centrifugal steam separators56 to which the present invention is applied.

[0025] The high temperature primary cooling water, which has cooled thereactor core in the nuclear reactor, is supplied to the primary coolingwater entrance chamber 53. The primary cooling water flows from theprimary cooling water entrance chamber 53 to the primary cooling wateroutlet chamber 55 through the tube bundle 54. On the other hand, thesecondary cooling water is directed to the periphery of the tube bundle54 in the pressure vessel 52 through a secondary cooling water inletport 52 b, provided in the pressure vessel 52, and a feed water ring 58.During the primary cooling water flows through the tube bundle 54, thesecondary cooling water contained in the pressure vessel 52 is heatedthrough the heat exchange with the primary cooling water. Thus, thesteam of the secondary cooling water is generated.

[0026] With reference to FIG. 4, a partial section of the moistureseparator 60 to which the present invention is applied is shown. Themoisture separator 60 (100-1500) has zigzag passages 68 of the inventiondisposed in a casing 62. The steam S, generated through the heatexchange with the primary cooling water as described above, flows fromthe lower side of a hood plate 64 through a plurality of apertures 66 a,defined in a perforated panel 66, and the passages 68 and out of theopposite side. During the steam S flows through the passages 68, thedroplets contained in the steam S are separated and returned through adrain pipe 70 to the lower part of the inside volume of the pressurevessel 52 where the secondary water is contained.

[0027] With reference to FIGS. 1 and 2, the passages 68 of the moistureseparator 60 will be described in detail below. In this connection, thepassages 68 are indicated by new reference numbers in the respectivefigures. Further, although only a single passage is shown in each ofFIGS. 1 and 2, the moisture separator 60 includes a plurality ofpassages disposed side by side and defined by a plurality of frameplates, as shown in FIG. 3.

[0028] The moisture separator 100 according a first embodiment shown inFIG. 1 includes a plurality of frame plates 102 which are disposedparallel to and separated from each other by spacers 126. Between theframe plates 102, a plurality of zigzag passages 101 are defined. Inparticular, a plurality of vanes or blades 104, 106, 108, 110, 112 and114 for defining the side walls of the passages 101 are attached to theframe plates 102. The vanes 104, 106, 108, 110, 112 and 114 form roots116 which swell outwardly relative to the passage 101 and apexes 118which swell inwardly relative to the passages 101. In this connection,in the embodiment of FIG. 1, the steam containing the droplets issupplied through the left end of each of the passages 101 and flows outof the moisture separator 100 through the right end. The terms“upstream”, “downstream” and “flow direction” are referred hereinafterin relation to this steam flow through the passages 101.

[0029] The vane 104 is disposed at the most upstream region and has abody portion 104 a defining a steam introducing section and a tailportion 104 b extending toward the apex 118. Each of the vane 106 has aflat body portion 106 a attached to the frame plate 102, a front portion106 b extending toward the apex 118 from the body portion 106 a, abending portion 106 c bending outwardly relative to the passage 101 fromthe front portion 106 b and a tail portion 106 d extending toward thedownstream apex 118 from the body portion 106 a. Each of the vanes 108has a body portion 108 a, a front portion 108 b, a bending portion 108 cand a tail portion 108 d. The vanes 108 are formed similar to the vanes106, however, the tail portions 108 d are longer that the tail portions106 d of the vanes 106. Each of the vanes 110 has a body portion 110 a,a front portion 110 b and a tail portion 110 c, however, does not has abending portion. Vanes 112 and 114 have flat body portions 112 a and 114a, defining a steam discharge section, and front portions 112 b and 114b extending to the upstream apexes 118. The body portions 104 a, 106 a,108 a, 110 a, 112 a and 114 a are arranged parallel to the frame plate102 and attached to the frame plate 102. This configuration enables thezigzag passages 101 to be defined between the frame plates 102 eventhough the frame plates 102 are flat.

[0030] The side walls, defined by the vanes 104, 106, 108, 110, 112 and114, in particular the side wall portions extending from the roots 116to the apexes 118, seen from the upstream side of the passage 101,define a plurality of openings 120 a and 112 a which provide entrancesof droplet collecting pockets 120 and 122. In this embodiment, thedroplet collecting pockets include first droplet collecting pockets 120for collecting relatively large droplets and second droplet collectingpockets 122, disposed in the passage 101 downstream of the first dropletcollecting pockets 120, for collecting relatively small droplets.

[0031] In this embodiment, the entrance openings 120 a of the firstdroplet collecting pockets 120 are arranged between the tail portion 104b of the vane 104 and the bending portion 106 c of one of the vanes 106and between the tail portions 106 d and the bending portions 108 c ofthe vanes 108. On the other hand, the entrance openings 122 a of thesecond droplet collecting pockets 122 are arranged between the tailportions 108 d of the vanes 108 and front portions 110 a of the vanes110 and between the tail portions 110 c of the vanes 110 and the frontportions 112 a and 114 a of the vanes 112 and 114.

[0032] As shown in FIG. 1, the entrance openings 120 a of the firstdroplet collecting pockets 120 are disposed apart from the apexes 118toward the roots 116 by a distance corresponding to the length of thebending portions 106 c and 108 c of the vanes 106 and 108. On the otherhand, the entrance openings 112 a of the second droplet collectingpockets 122 are disposed to adjoin the apexes 118 because the vanes 110,112 and 114 do not have portions extending from the apexes 118 towardthe upstream side roots 116.

[0033] The operations and functions of this embodiment will be describedbelow.

[0034] The steam containing the droplets flows into the passages 101through the left ends of the passages in FIG. 1. When the steam flowsthrough the zigzag passages 101, the droplets contained in the steamimpinge against the side walls of the passages 101. At that time, aportion of the droplets enters into the first droplet collecting pockets120 and 122 to be trapped in the pocket 120 and 122. The dropletstrapped in the pockets 120 and 122 are collected into a drain recoveryunit (not shown) and mixed into the secondary cooling water contained inthe steam generator.

[0035] In the upstream side of the passage 101, most of the relativelylarge droplets are trapped. Therefore, the droplet collecting pocketsare saturated with water, and so called carry over easily occurs toallow droplets fly again into the steam flow in the passage 101. Inparticular, stagnation flows are generated adjacent the roots 116 sothat the main stream in the passages 101 passes over the stagnationflows. Therefore, the trapped water is often lodged unevenly at thedownstream side from the apexes 118 within the inside volume of thefirst droplet collecting pockets 120. Therefore, the bending portions106 c and 108 c of the vanes 106 and 108 are provided at the entranceopenings 120 a of the first droplet collecting pockets 120, which aredisposed at the upstream side portions of the passages 101, to reducethe unevenly lodged water and to prevent the carry over. Further, theentrance openings 120 a of the first droplet collecting pockets 120 areadvantageously disposed near the apexes 118 apart from the stagnationflows.

[0036] On the other hand, at the downstream side portions of thepassages 101, a large number of relatively small droplets are containedin the steam flow. The smaller the droplets, the more likely they rideon the steam flow and do not impinge against the side walls. Therefore,the entrance openings 122 a of the second droplet collecting pockets 122are adjoining the apexes 118, where the flow rate is high and the flowdirection is suddenly changed, to promote the collection of the smalldroplets.

[0037] With reference to FIG. 2, a second embodiment of the inventionwill be described below.

[0038] The moisture separator 200 according a second embodiment shown inFIG. 2 includes a plurality of frame plates 202 which are disposedparallel to and separated from each other by spacers 224. Between theframe plates 202, a plurality of zigzag passages 201 are defined. Inparticular, a plurality of vanes or blades 204, 206, 208, 210, 212 and214 for defining the side walls of the passages 201 are attached to theframe plates 202. The vanes 204, 206, 208, 210, 212 and 214 form roots216 which swell outwardly relative to the passage 201 and apexes 218which swell inwardly relative to the passages 201. In this connection,in the embodiment of FIG. 2, the steam containing the droplets is alsosupplied through the left end of each of the passages 201 and flows outof the moisture separator 200 through the right end. The terms“upstream” “downstream” and “flow direction” are referred hereinafter inrelation to this steam flow through the passages 201.

[0039] The vane 204 is disposed at the most upstream region and has abody portion 204 a defining a steam introducing section and a tailportion 204 b extending toward the apex 218. Each of the vane 206 has aflat body portion 206 a attached to the frame plate 202, a front portion206 b extending toward the apex 218 from the body portion 206 a, anintermediate portion 206 c extending parallel to the frame plate 202from the front portion 206 b, a bending portion 206 d bending outwardlyrelative to the passage 201 from the intermediate portion 206 c and atail portion 206 e extending toward the downstream apex 218 from thebody portion 206 a. Each of the vanes 208 has a body portion 208 a, afront portion 208 b, an intermediate portion 208 c, a bending portion208 d and a tail portion 208 e. The vanes 208 are formed similar to thevanes 206, however, the tail portions 208 e are longer that the tailportions 206 d of the vanes 206. Each of the vanes 210 has a bodyportion 210 a, a front portion 210 b and a tail portion 210 c, however,does not has an intermediate portion and a bending portion. Vanes 212and 214 have flat body portions 212 a and 214 a, defining a steamdischarge section, and front portions 212 b and 214 b extending to theupstream apexes 218. The body portions 204 a, 206 a, 208 a, 210 a, 212 aand 214 a are arranged parallel to the frame plate 202 and attached tothe frame plate 202. This configuration enables the zigzag passages 201to be defined between the frame plates 202 even though the frame plates202 are flat.

[0040] The side walls, defined by the vanes 204, 206, 208, 220, 212 and214, in particular the side wall portions extending from the roots 216to the apexes 218, seen from the upstream side of the passage 201,define a plurality of openings 220 a and 212 a which provide entrancesof droplet collecting pockets 220 and 222. In this embodiment, thedroplet collecting pockets include first droplet collecting pockets 220for collecting relatively large droplets and second droplet collectingpockets 222, disposed in the passage 201 downstream of the first dropletcollecting pockets 220, for collecting relatively small droplets.

[0041] In this embodiment, the entrance openings 220 a of the firstdroplet collecting pockets 220 are arranged between the tail portion 204b of the vane 204 and the bending portion 206 d of one of the vanes 206and between the tail portions 206 e and the bending portions 208 d ofthe vanes 208. On the other hand, the entrance openings 222 a of thesecond droplet collecting pockets 222 are arranged between the tailportions 208 e of the vanes 208 and front portions 210 a of the vanes210 and the tail portions 210 c of the vanes 210 and the front portions212 a and 214 a of the vanes 212 and 214.

[0042] As described above, the second embodiment is substantiallyidentical to the first embodiment, except for that the vanes 206 and 208have intermediate portions 206 c and 208 c. Therefore, the operation andeffect of the second embodiment is substantially identical to those ofthe first embodiment. However, according to the second embodiment, theprovision of the intermediate portions 206 c and 208 c reduces thepressure loss of the steam through the passages 201.

[0043] Further, in the above-described embodiments, the vanes havesectional configurations composed of lines connected to each other.However, the vanes may have sectional configurations composed of arcuatesections connected to each other.

[0044] Further, a droplet collecting member, for example a coil memberor a perforating plate for promoting the agglomeration of the droplets,may be disposed between the first and second droplet collecting pockets.

1. A moisture separator comprising a plurality of flat frame platesdisposed parallel to each other to define a plurality of zigzag passagesbetween the frame plates, side walls facing the upstream side of thepassages defining entrance openings of droplet collecting pockets.
 2. Amoisture separator with a plurality of frame plates disposed parallel toeach other to define a plurality of zigzag passages, wherein the frameplates comprise flat plate members; the moisture separator comprisingdroplet collecting pockets having entrance openings disposed in sidewall portions of the zigzag passages between, seeing from the upstreamside of the passages, roots swelling outwardly relative to the passageand apexes swelling inwardly relative to the passage; and the dropletcollecting pocket including first droplet collecting pockets, disposedat the upstream side of the passages, for collecting relatively largedroplets, and second droplet collecting pockets, disposed at thedownstream side of the passages, for collecting relatively smalldroplets.
 3. A moisture separator according to claim 2, wherein theentrance openings of the first droplet collecting pockets are disposedapart from the apexes in the side wall portions between the rootsswelling outwardly relative to the passage and the apexes swellinginwardly relative to the passage, and the entrance openings of thesecond droplet collecting pockets are disposed adjacent the apexes inthe side wall portions between the roots swelling outwardly relative tothe passage and the apexes swelling inwardly relative to the passage. 4.A moisture separator according to claim 2 or 3 further comprising means,disposed between the first and second droplet collecting pockets, foragglomerating droplets.
 5. A moisture separator according to claim 4,wherein the means for agglomerating droplets comprises a coil memberdisposed to across the passage.
 6. A moisture separator with a pluralityof frame plates disposed parallel to each other to define a plurality ofzigzag passages, wherein the frame plates comprise flat plate members;the moisture separator comprising a plurality of droplet collectingpockets having entrance openings disposed in side wall portions of thezigzag passages between, seeing from the upstream side of the passages,roots swelling outwardly relative to the passage and apexes swellinginwardly relative to the passage; and the entrance openings of all thedroplet collecting pocket being disposed adjacent the apexes in the sidewall portions between the roots swelling outwardly relative to thepassage and the apexes swelling inwardly relative to the passage.
 7. Amoisture separator according to claim 6, wherein the zigzag passages aredefined by a plurality of vanes secured to the frame plates, the mostupstream vanes of the plurality of vanes have projections extendingalong the central axis in the upstream direction relative to the steamflow through the passages toward a steam introducing section.
 8. Amoisture separator with a plurality of frame plates disposed parallel toeach other and a plurality of arcuate sections attached to the frameplates to define a plurality of serpentine passages, wherein the frameplates comprise flat plate members; the moisture separator comprising aplurality of droplet collecting pockets having entrance openingsdisposed in side wall portions of the serpentine passages between,seeing from the upstream side of the passages, roots swelling outwardlyrelative to the passage and apexes swelling inwardly relative to thepassage.
 9. A moisture separator according to claim 8, wherein theserpentine passages are defined by a plurality of vanes secured to theframe plates, the plurality of vanes including arcuately curved portionsdisposed at least the either end thereof.
 10. A steam generatorcomprising a moisture separator according to any one of the precedingclaims, an inversed U-shaped tube bundle which uses the primary coolingwater from a nuclear reactor as a heating medium and a plurality of stemseparators.